Room: Karl Dean Ballroom C
Purpose: To bridge anatomic, biologic, and functional information for individualizing oncologic therapy in sarcoma patients. Anatomic imaging (CT, MRI) assists in target volume definition and therapy response assessment, however, there is no predictive technique for RT response of sarcomas. To leverage the advantages of biological- and physiological-based imaging techniques, we studied the use of magnetic resonance elastography (MRE) and DCE-MRI to quantify early changes in tumor mechanical properties and perfusion in sarcomas to serve as a surrogate of pathologic response.
Methods: 25 sarcoma patients were enrolled in an IRB-approved study. Imaging was performed before, during (3 time-points), and after radiotherapy. Tumor stiffness was evaluated using a 3D-GRE MRE sequence and stiffness map (3D local frequency estimation inversion). Tissue perfusion was assessed using a T1-weighted 3D time-resolved DCE-MRI sequence, and quantitative parameters (Ktrans, kep) were computed. Images were registered to treatment planning MRIs to obtain contours (GTV) used for ROIs. Surgical resection was performed in 15 patients for imaging to pathology correlations, reporting tumor % necrosis, % viable, and % fibrosis.
Results: Preliminary analysis shows MRE and DCE-MRI can quantitatively assess change in stiffness and perfusion in sarcomas after completion of radiotherapy. Heterogeneous changes in stiffness and perfusion were observed, corresponding to decreases in tumor volume and pathologic findings of fibrosis, necrosis, and viable tumor. For example, in a patient with myxofibrosarcoma, a 6% decrease in stiffness from baseline to presurgery was observed and corresponded to 83% viable tumor. Alternatively, in a patient with pleomorphic sarcoma, a 12% decrease was observed at 8 days and 20% at 2 months, with only 20% viable tumor at surgery.
Conclusion: Tumor stiffness and perfusion changes quantified using MRE and DCE-MRI following RT in sarcomas and may improve the ability to noninvasively determine response to therapy and efficiently evaluate novel therapies.
Funding Support, Disclosures, and Conflict of Interest: Partial funding for this work was provided by Varian.
Not Applicable / None Entered.